Apparatus for the separation of gaseous mixtures



March 14, 1950 2,500,240

APPARATUS FOR THE SEPARATION OF GASEOUS MIXTURES J. R. BowMAN Filed May l, 1945 Patented Mar. 14, 1950 s PATENT OFFICE APPARATUS FOR THE SEPARATION OF GASEOUS MIXTURES John R. Bowman, Pittsburgh, Pa., assigner to Gulf Research & Development Company, a corporation of Delaware .Application May 1, 1945, Serial No. 591,381

(Cl. 18S- 2) 1 Claim. l

This invention relates to apparatus for the separating of materials, and more particularly to an apparatus for the separation of homogeneous single phase mixtures.

The separation of homogeneous single phase mixtures has been accomplished in various ways dependent upon the particular mixtures to be separated. These methods include distillation, diffusion, extraction, absorption, adsorption, fractional recrystallization, etc.

These separatory processes are all susceptible of improvement, primarily in overall economy or in ability to separate two or more materials whose physical properties make them difficult to separate. In the case of diffusion, particularly of gases, for example, methods have not been evolved which are capable of extensive commercial use, primarily because the gas passing through the diffusion membrane is not substantially pure and thus efficient separation has not been attained.

In the case of distillation, it has been a more recent practice to use methods in which there is rectiiication or intermediate enrichment of the vapor,v usually effected in a rectifying column, such as a bubble plate rectifier, packed tower, or Steadman still. These methods, however, fail under certain operating conditions, such as under high vacuum, and the need has been recognized for a rectifying method operable at high vacuum in an efficient manner. f

In general, the prior methods of separation of homogeneous single phase mixtures have depended upon countercurrent contacting.

In accordance with the present invention, I have provided an apparatus for the separation of homogeneous single phase mixtures not using countercurrent contacting, the operation of said apparatus comprising establishing a mainstream of the mixture, removing a plurality of side streams from the main stream having different compositions from the main stream at their respective points of origin andreturning these side streams out of contact with the main stream to the main stream at points where the compositions of the two are substantially equal.

By way of illustration of a specific utilization of my apparatus, two gases such as hydrogen and methane in admixture may be passed longitudinally through a tube of permeable material about which are separated segmented chambers. The gas which diffuses into each chamber is richer in hydrogen than the gas in the stream just outside the chamber. This gas is removed from the chamber and reintroduced to the main stream at a point upstream from its origin where the hydrogen and methane ratio is about the same as the gas removed from the chamber. Repeated operation in a plurality of chambers causes an enrichment of the gases downstream, so that almost pure methane can be obtained from the downstream end of the tube and at the same time a gas quite rich in hydrogen is obtained in the most upstream chamber. The apparatus for applying this method will be described below in detail.

In the accompanying drawings:

Figure 1 is a, diagrammatic showing of the invention broadly; y

Figure 2 is a view in section of a diffusion apparatus;

Figure 3 is a view in section of an. alternative diffusion apparatus.

In Figure 1 there is shown diagrammatically the general concept of the invention. Line Ill represents a main stream of a single phase homogeneous mixture flowing as indicated by the arrows. Line I I indicates the feed line and line I2 indicates the end of the main stream where the product is substantially freed from one or more of its components. Curved lines I3 indicate that a part of the main stream is taken off with change in composition at the point of origin and returned to the main stream at a point upstream. In the flow diagram it is not possible to show thatat the point at which material is taken oi from the main stream, there should be a device for changing the composition of thek mixture, so that the material in the side stream is of a different composition fromy the material in the main stream at the point where the side stream emerges. This device may be a diffusion membrane or a heated plate, as will be illustrated below, or other device for accomplishing a separation as described. One of the components is taken on at point I4 and the other component is taken off at the end I2 of the main stream. Feed may be introduced at the entrance end of the main stream instead of at line I I.

With reference to Figure 2, there is illustrated an apparatus for carrying out the invention as specically applied to diffusion. The device illustrated is adapted to the removal, for example, of hydrogen from a methane-hydrogen mixture. A cylinder I5, preferably of heavy steel, contains a conduit I6 at its upper end and concentrically arranged therein is a cylindrical tube I1 of permeable material, such as porous clay. The space between tube I 1 and the outer walls of cylinder I5 is divided into compartments or cells pumps 23 tocausethe ow of gasfrom the cells I8 to theA permeable tube I'I.

In the operation of this device, the gas mixture enters the cylinder I5 by means of conduit I6 and.;

passes down the permeable tube I'I vand out lof the conduit 25. In so doing, a part ofl the mixturek richer in hydrogen than the main stream at the respective points of origin difiusesthrough the.

walls of porous cylinder I'I and enters Aeaclii olf-I'lliefv cells I8. This diffused gas is returned to points upstream from the cell in whichhit was extracted. These points may be calculated or determined by test and for best separation, shouldfbe the` point at which the concentrations of hydrogen in the conduits 2| andin themain stream at points 22 are respectively substantially equal. The, gas, rich in hydrogen, which-isY collected in the` uppermost cell passes outof conduit 26 and is collected for use where^ gases rich, .in hydrogen. are desirable or may lbe in part reintroduced with the original mixture. It will be seen-that as themain stream moves downward. it loses more and more of` its hydrogen, until a` glas comprising substantially pure methane is removed at conduit 25, By this method it is possible to obtain a product containing about 99 per cent methane 'and 1 percent hydrogen rfrom the conduit 25 anda product containing about 20 per cent methaneand 80-per cent hydrogen from the conduit. 26, starting with a feed containing 50 per cent hydrogen.

In Figure 3 thereis shownan alternativedevice to Figure 2, in which conduits 2V8.similar in function to cond-uitl 2I of Figure 2 are placed inside of the outer steel cylinder I5 and vextend entirely within porous tube I'I. In this manner there is no high pressure differential in these conduits and pumps 29 may be. easily installed in the side walls` terals but it will be understood thatthe separas tion is only partial or. an` enrichment. The separationA of two components from each. other by this method may result, in two products, one enriched greatly in the iirst` component and the other enriched slightly in the. second component or both products may be greatly enriched, one in therrst component and the other in the second component, depending upon the point at` which the feed enters. As described with reference to Figure 1 the feed may be at thebeginning of the main 4 stream or at an intermediate point. This applies to each of the devices illustrated.

Thus, I have described an apparatus for the separation of single phase homogeneous mixtures wherein a main stream of the mixture is established and a plurality of side streams removed having. different compositions from the main stream at the respectivef points of origin and wherein the side streams are returned to the main stream at points where the composition of the mainstream and the side streams are substantelly. Squall What I claim is:

Apparatusior separation of gaseous mixtures comprising an elongated shell having an inlet and an outlet atits ends, end partitions within the shell deiining chambers adjacent to the inlet and outle'tQa conduit of permeable material extending betweenthe end partitions and opening into said chambers, a series of additional partitions eX- tendingfrom the.y wall ofA theshell and surrounding'said conduit thereby forming separate cells each having a permeable wall formed by a portion of the said conduit, means for introducing a gaseous mixture at the4 inlet of the shell whereby as it flows through the permeableconduit toward the outlet diffusion occurs into the several cells, the diffusate being'rich'er. in lthe gaseous component of greatest dffusibility, pipes extending from the respective cells. toA upstream points in 'y the permeable conduit :at which the composition IiIl ofthe diiusate so introduced is substantially the same as thatof the main stream at the point of their mixing, means for re'si'ga'blishing ow of diffusate from said cellsvthrough said pipes, the said outlet from saidshell providing l'means for with; drawal of the least' diiusible component of the gaseous mixture, and' aseicond outlet communicating with a cell remote from the rst said outlet for removing the gaseous component of greater dilusibility.

JOHN R. BQWMAN.

REFERENCES CITED The following references are of record in the yfile of this patenti UNITED sTATEs PATENTS OTHER, REFERENCES Separation Processes, Randell et al.: Id. Eng. Chem.`, Jan. 1940, vol. 3,2, No. l, pp. 125-129. 

